The present invention relates to an inclination sensor which detects the inclination angle of an object on which the sensor is placed.
An inclination sensor may be used in various objects such as in measuring devices, cars, and planes for detecting the inclination angle thereof. A conventional inclination sensor includes a container in which a liquid and a gas Are sealed such that the gas forms a bubble floating in the liquid. The inclination sensor is then arranged to electrically detect the position of the bubble and thereby detect the inclination of the object on which the inclination sensor is placed.
FIG. 1 shows an example of an inclination sensor as disclosed in Japanese Patent Laid-Open Publication No. HEI 7-146142. A container 65 includes a top plate 60, a bottom plate 62, and a cylindrical wall 61 between the top and bottom plates 60 and 62. A liquid L and a bubble B are sealed inside the container 65. A bottom surface of the top plate 60 is formed to provide a spherical concave surface.
A first top electrode 63a and a second top electrode 63b are attached to the top plate 60 and a bottom electrode 64 is attached to the bottom plate 62 in such a manner that the liquid L is in contact with the electrodes 63a, 63b, and 64. The first and second top electrodes 63a and 63b are attached to opposite sides (the left and right in FIG. 1) of the top plate 60, respectively, with a space therebetween.
The contact area of the liquid L with respect to the first top electrode 63a and the second top electrode 63b changes according to the inclination of the container 65 in a direction in which an inclination is to be measured (a measuring direction: shown by X in FIG. 1). Accordingly, when a voltage is applied to the electrodes 63a, 63b, and 64, a ratio of the current flow through the first top electrode 63a and the bottom electrode 64 to the current flow through the second top electrode 63b and the bottom electrode 64 varies according to the inclination of the container 65. Accordingly, the inclination of the container 65 may be detected by measuring the current flow.
However, since the bottom surface of the top plate 60 is a spherical concave surface, if the container 65 is inclined with respect to a direction perpendicular to the measuring direction, the bubble B may move toward and come in contact with the cylindrical wall 61, which would affect the detection of the inclination. Accordingly, it is necessary to keep the container 65 precisely level with respect to the direction perpendicular to the measuring direction in order to provide accurate measurement.